Year 3 Science: Contact and magnetic forces
Part of the Year 3 Science forces chapter. Chapter overview · whole chapter on one page
Contact and magnetic forces
Most forces need contact. This means the two objects must touch. When your hand pushes a box, your hand touches the box, and the force acts through that contact.
Magnetic forces are different. A magnet can pull a steel paper clip across a small gap, without touching it. We say that magnetic forces can act at a distance.
The table shows six actions. Some need the two objects to touch, and some do not.
| Action | Do the two objects need to touch? |
|---|---|
| A hand pushes a toy car across a table | yes |
| A magnet pulls a steel paper clip across a small gap | no |
| A rope pulls a sledge up a snowy hill | yes |
| A foot kicks a football | yes |
| A book slows and stops on a table because of rubbing | yes |
| A magnet pulls a steel nail across a small gap | no |
Key ideas
- Many forces need contact: the two objects must touch.
- Magnetic forces can act at a distance, so a magnet can pull a steel paper clip across a small gap.
- A push, a pull and friction all need the objects to touch.
- A steel nail can also be pulled by a magnet across a small gap.
Method. Find the row about the rope.
- Find the row. The row says a rope pulls a sledge up a snowy hill.rope and sledge
- Read the answer. The answer in the second column is yes.yes
- Write the answer. yes
Check. The rope must be attached to the sledge for the pull to work. ✓
Method. Find the row about the steel nail.
- Find the row. The row says a magnet pulls a steel nail across a small gap.steel nail
- Read the answer. The answer in the second column is no.no
- Write the answer. no
Check. A magnetic force can act at a distance. ✓
Method. Count the rows that say yes.
- Read the second column. The rows that say yes are the hand and toy car, the rope and sledge, the foot and football, and the book on the table.four yes
- Count them. There are four actions that need contact.4
- Write the answer. 4
Check. The two magnet rows say no. ✓
Watch out
Watch out: a magnetic force can act at a distance, but most other forces, such as a push, a pull or friction, need the objects to touch.
Try it at home or school (with a grown-up). With a grown-up, hold a magnet near a steel paper clip on a table, and move the magnet slowly until the clip moves. Notice how close the magnet must be. Then push a small toy with your finger, and notice that your finger must touch it. Keep magnets away from your mouth, and away from phones and bank cards.
Exam tip
Grown-up tip. Ask: “Did the magnet and the clip touch? Did your finger touch the toy?” Let your child use the words contact and act at a distance.
Exercise 9C Contact and magnetic forces
Method. Think about the push.
- Think about the hand and the box. The hand must touch the box to push it.touch
- Decide. So the answer is yes.yes
- Write the answer. yes
Check. Pushing needs contact between the two objects. ✓
Method. Think about magnetic forces.
- Think about the magnet. Magnetic forces can act at a distance, so the magnet does not need to touch the clip.at a distance
- Decide. So the answer is yes.yes
- Write the answer. yes
Check. The clip moves across the gap without being touched. ✓
Method. Read the key idea in section 9.3.
- Read the key idea. Magnetic forces can act at a distance.distance
- Write the answer. distance
Check. A distance means a gap between the objects. ✓
Method. Read the key idea in section 9.3.
- Read the key idea. Many forces need contact, which means the two objects must touch.contact
- Write the answer. contact
Check. Contact means touching. ✓
Method. Find the row about the football.
- Find the row. The row says a foot kicks a football.foot and football
- Read the answer. The answer in the second column is yes.yes
- Write the answer. yes
Check. The foot must touch the ball to kick it. ✓
Method. Count the yes rows.
- Read the second column. Four rows say yes, and two rows say no.four yes
- Count them. So four actions need contact.4
- Write the answer. 4
Check. Six actions, with two that do not need contact, make four. ✓
Method. Find the row with the steel nail.
- Read the first column. The row says a magnet pulls a steel nail across a small gap.steel nail
- Write the answer. A magnet pulls a steel nail across a small gap
Check. This action does not need contact. ✓
Method. Think about the rope.
- Think about the rope. The rope is tied to the sledge, so it touches the sledge.tied to
- Decide. So the answer is yes.yes
- Write the answer. yes
Check. A rope pulls the sledge through contact. ✓
Method. Think about the magnet.
- Think about the magnet. A magnetic force can act at a distance, so contact is not needed for every force.at a distance
- Decide. So Priya is not right.no
- Write the answer. no
Check. Some forces need contact, and some do not. ✓
Method. Think about what makes a test fair.
- Think about the test. Only the distance you measure should change; the magnet, the clip and the table must stay the same.stay the same
- Write one thing. For example, use the same magnet each time.same magnet
- Write the answer. Accept any one of: the same magnet, the same paper clip, the same table.
Check. Keep everything else the same, so that the test is fair. ✓
Method. Think about each force.
- Think about the magnet. A magnetic force can act at a distance across a small gap.at a distance
- Think about the hand. A push needs contact, so the hand must touch the box.contact
- Write the answer. Accept any sentence that says a magnetic force can act at a distance, but a push needs the hand and the box to touch.
Check. Magnetic forces are one of the special cases: most forces need contact. ✓